A well-known retractable ballpoint pen is provided with a ballpoint pen refill having a ballpoint pen tip capable of being projected from and retracted into a barrel through an open forward end of the barrel. This retractable ballpoint pen has a ballpoint pen refill containing writing ink which is inserted in the barrel for sliding movement in the barrel and biased toward the rear end of the barrel by a spring. This retractable ballpoint pen has a retracting mechanism for projecting the ballpoint pen tip from and retracting the same into the barrel through the open forward end of the barrel.
A retractable ballpoint pen with a ballpoint pen refill having an ink-accommodating tube containing water-based ink has been marketed in recent years.
The ballpoint pen tip of the retractable ballpoint pen with the ballpoint pen refill having the ink-accommodating tube containing water-based ink is pointed downward when the retractable ballpoint pen is held in a pocket of clothes with a clip. Consequently, problems are liable to arise due to leakage or back-flow of ink. Back-flow of ink is a phenomenon in which the ink flows rearward from the ballpoint pen tip into the ink-accommodating tube due to shocks caused by the operation of a retracting mechanism or dropping.
The present invention has been made in view of the above-mentioned problems. It is therefore an object of the present invention to provide a retractable ballpoint pen with a ballpoint pen refill having an ink-accommodating tube containing water-based ink inserted in a barrel. The pen is free of ink leakage from its tip and free of ink back-flow due to shocks caused by retractable operation, and the pen is also satisfactory in writing performance.